BIOLOGY. 309 



egg, he ascertained that the results obtained depended on another 

 cause ; and he turned his attention to artilicial incubation, applyino* 

 the heat to a single point. If, instead of applying the heat directly 

 to the point of the egg, where the cicatricnla is always placed at 

 the couiniencement of development, we heat a point distant from 

 this, the evolution is always disturbed, and an anomaly caused at 

 first in the form of the blastoderm and then in the vascular area. 

 Under these conditions the development of the cicatricula occurs 

 much more in the region between the point of the egg and the 

 point of contact with the source of heat than in the opposite re- 

 gion. Hence, the blastoderm and then the vascular area take ou 

 an elliptical form, and the embr3'o is developed in one of the foci 

 of the ellipse ; while in the normal condition the embryo occuj^ies 

 the centre of a perfectly circular blastoderm and vascular area. 

 This abnormal development can be directed to any side according 

 to tiie application of the heat. These results are evident disturb- 

 ances of evolution, and not, as M. CI. Bernard thinks, simple 

 pathological changes. 



Tiie embryos which appear in these deformed blastoderms are 

 very often monstrous, and among them maj' be recognized, in pro- 

 cess of formation, almost all the types of simple monstrosity de- 

 scribed by I. Geoffroy St. Hilaire, and sometimes also forms un- 

 known to him, as that characterized by the existence of a double 

 heart. 



In a previous communication to the Academy he had shown 

 that celosomy, exencephaly, and ectiomely, so often asssociated, 

 result from the arrested development of the amnios ; that anen- 

 cephaly is produced by a dropsy consequent on an alteration of the 

 blood ; that the inversion of the viscera is explained by the pre- 

 dominance of one of the two hearts which he had discovered exist 

 normally at a certain epoch of embryonic life. He also shows 

 that symely results from an arrest of development of the caudal 

 hood of the amnios, and cyclopy from arrested development of the 

 cephalic hood of this organ. All these anomalies are essentially 

 characterized by disturbances of evolution, and in none, anen- 

 cephaly excepted, is there any pathological change to modify the 

 development. He has ascertained that incubation of the eggs at 

 a temperature higher than 40 degrees often produces dwarfed 

 development. 



He accepts Cruveilhier^s explanation of S3miely, or the inversion 

 and fusion of the posterior limbs, by rotation and lateral pressure 

 in the early period of intra-uterine life ; but adds that the cause of 

 this pressure is an arrest of development of the posterior or caudal 

 extremity of the amnios, it remaining applied against the poste- 

 rior part of the body instead of being separated from it by the 

 amniotic liquid, and consequently inverting and pressing together 

 the external surfaces of the bud-like posterior limbs, — forming a 

 veritable graft by approximation. What determines this want of 

 parallelism between the embr3'o and the amnios, and the arrest 

 of development of its posterior portion, future researches must 

 determine. 



In this way the development may be augmented in any direc- 



